Numerous devices are known in the art for freezing frozen confections, particularly frozen confections containing sticks so that the confections may be held by the stick while being eaten. Most of the devices are similarly configured, comprising a large number of inverted molds on a conveyor. The molds are conveyed past a suitable filling apparatus and into a freezing zone wherein a refrigerated liquid is typically contacted with the outsides of the mold to freeze the contents. At a pre-determined point in the freezing zone, sticks are inserted into the then partially frozen contents of the mold. The frozen confections are discharged from the molds upon exiting the freezing zone. In most instances, the confections are simply packaged and storaged for later consumption. In other instances, such as for pudding-based or gelatin-based frozed confections, the confections are dipped in a water bath to form an encapsulating ice shell in order to prevent dehydration of the produce upon storage. If the confections are not thoroughly frozen prior to being dipped in the water bath, the ice coating will not form properly, giving rise to the possibility of dehydration. The problem is particularly acute for the top part of the confection which is typically exposed to ambient air.
While it is possible to insure thorough freezing of the entire confection by constructing a freezing unit of greater capacity of lengthening the residence time of the molds in the freezing zone, such as by slowing down the conveyor, such alternatives are not commercially optimal. The aforementioned freezing units are most often marketed according to only one set of specifications, typically adapted to the freezing of ice cream, and customizing the unit by requiring greater freezing capacity is prohibitively expensive. Moreover, slowing down the conveyor is equally impractical because of the desired level of productivity, preferably in excess of 20 cycles per minute. Thus, some other method of achieving acceptable productivity while insuring thorough freezing of the entire frozen confection must be used.
The use of liquid nitrogen and other liquid cryogens for freezing foods is known in the art. For instance, U.S. Pat. No. 3,114,248 to Morrison discloses placing a food in an open-face pan, sprinkling the surface with liquid nitrogen to form a frozen crust thereon and subsequently immersing the whole pan in liquid nitrogen to rapidly freeze the contents. It is known, however, that such rapid freezing leads to the formation of very fine ice crystals. Such fine ice crystals are undesirable in most frozen confections in which it is most preferable to have an ice crystal size between 10 and 150 microns. Thus, the exclusive use of a liquid cryogen is not practical for increasing the productivity of freezing frozen confections.
It is an object of the present invention to provide a method for continuously producing pop-shaped frozen confections at line speeds exceeding 20 cycles per minute.